Last week, I went out for one of my traditional Threshold rides. The workout was eight minutes at threshold with four minutes rest, repeat four times. It was nothing new to me, as I was in the middle of a nice threshold build block. The ride started out great. After my warm up, I headed to the hills to do my intervals. I find hills helpful for longer threshold efforts. My first interval went pretty well. I kept the power where it needed to be, but as I got towards the end, I noticed my heart rate was higher than it should be. However, when I started my second interval, something was clearly wrong. I was barely able to stay close to my power target and my heart rate was 95% of max. I quickly realized that I messed up one key thing: heat adaptation.
The irony was, heat adaptation was all anyone was talking about going into the Olympics. In fact, even the USA Crits series was dealing with this same issue because most of the crits thus far have been extremely hot. I had done some heat adaptation towards the end of July, but clearly I had made some mistakes.
What is heat adaptation?
Heat adaptation (or acclimation) is a relatively straightforward term, and one that most endurance athletes are familiar with. The formal definition is as follows:
Heat adaptation confers biological adaptations that reduce physiological strain (e.g., heart rate and body temperature), improve comfort, improve exercise capacity and reduce the risks of serious heat illness during exposure to heat stress.
When applied to cycling, it’s the ability of our body to perform efficiently and effectively at high temperatures and/or humidity.
Why does heat adaptation matter?
In my introduction, I gave an example of training in the heat and failing to properly adapt to the heat. While blowing up in training is one thing, being unable to complete a race, or do as well as you hoped, is a much greater issue. No matter what someone says – “I’m great at racing when it’s hot” or “I’m terrible in the heat” – heat adaptation matters and does impair one’s ability to perform optimally.
Not only does heat impair performance, it can affect it at a much lower temperature than we may think. An analysis of multiple marathons across a variety of locations showed that even at 10°C times where impaired (Ely et al. 2007). The 2007 study also showed that the less fit you were, the greater the impact of the heat on performance. Anecdotally, I think these studies do not correlate to cycling itself for a variety of reasons. I mention this study because it’s important to note that there may be a decrease in performance before you reach a point where you “feel hot”.
A more relevant, and interesting study, came out of the 2016 Road Cycling World Championships in Doha, Qatar. During the event temperatures reached nearly 40°C (104°F). The study determined that 34 riders (out of 40) reached a core temperature of 39°C. 10 of those riders core temperature exceeded 40°C. As one might expect, higher core temperatures occurred in the time trial (ITT) and team time trial (TTT) versus the road race (RR). The highest temperature recorded (in the TTT) was 41.5°C (106.7°F) (Racinais et al, 2018).
The study also took a look at power output and heart rate amongst those same riders. They noticed that power output was significantly higher during the TTT (4.7±0.3W/kg) and ITT (4.9±0.5W/kg), than the RR (2.7±0.4W/kg, p<0.001). Heart rate also increased during the TTs (p<0.001) while power output decreased (p<0.001). The bottom line is that not matter what level you’re riding at, or event you do, higher temperatures have a significant effect on the body, and thus performance.
Heat adaptation methods
In reality, heat adaptation is a relatively simple process. Over a period of time (ideally 10 – 14 days), you increase your body’s exposure to hot conditions. This adaptation enablesyou to perform better in the heat than you normally would. It should be noted that performance will still likely be diminished from what you might have done in cooler conditions. The performance improvement is primarily do to:
- Increased sweating response
- Improved skin blood flow response
- Increase blood volume due to the increase in plasma volume
- Improved fluid-electrolyte balance
Adapt like a pro
United States Olympic Facility
One of the more fascinating things I heard about this summer was the altitude chamber at the USOC. Obviously, any top notch olympic facility should have the best of the best, but I learned that the chamber cannot only dial in a specific altitude, it is also temperature and humidity controlled. Obviously this would be the best way to adapt, but, if you’re not an Olympian or able to build a facility to house the chamber, you can go the Tom Pidcock route.
Tom Pidcock and the “Heat Tent”
Heading into the Olympic MTB race, Tom Pidcock knew the heat and humidity would be one of the biggest factors. As a result, he built a “heat tent” where he would spend 30 – 45 minutes after each ride spinning slowly on a trainer. While talent and skill obviously contributed to Pidcock’s ride, his method of heat adaptation also helped propel him to victory in Tokyo.
Practical methods for adaptation
Most of us do not have access to an Olympic Facility or even a decent heat tent setup (even Pidcock’s setup kept tripping the electricity) – so what can we do? A very simple method is to do endurance and/or tempro rides in leg warmers and arm warmers. Some riders will even use thermal bibs and leg warmers to increase the heat a bit more. Similar to Pidcock, another widely used method is hopping in a sauna for 20-30 minutes after a ride. While Pidcock would spin his legs out, you can get some similar adaptations from simply sitting in a sauna after a ride. Another option is to get out in the heat (ideally around mid-day) and do a nice endurance ride. All of the aforementioned options will help a rider adapt to hot conditions.
Note: these are just a few proven methods. I personally do not recommend one over the other. I would also advise you to be very careful not to overdo it. For instance, doing a Zwift race inside a camping tent with a kerosene heater is probably a bad idea.
When to do begin adapting
As mentioned earlier, the ideally time to begin heat adaptation is roughly two weeks out from your event. You do not have to train for heat adaptation every day. Most, if not all, high intensity rides should be done in cooler conditions as you slowly adapt. During this period workouts in hot conditions should be at a lower-than-normal intensity. After a couple of weeks you will begin to perform better in the heat.
Circling back to the beginning of this article, I could have performed my threshold workout in the hot conditions if I backed off the intensity and/or did shorter intervals. There are two things I could have done to get the same physiological benefits of the workout while increasing my heat adaptation.
One option would have been to do the intervals at a lower power. Rather than riding at 100% of FTP, I could have backed it off to 94-95%. So, if my lactate threshold is 300 watts at 73°F, I could reduce it by 6.5% (Tatterson et al, 2000) to 280 watts when it’s 90 degrees.
Another option would be to reduce the length of each interval. Ultimately, the workout was designed to spend 32 minutes at threshold. Rather than do four eight-minute intervals, I could have done five six-minute intervals. The rest would stay at four-minutes between each interval. This would equate to 30 minutes at threshold and those extra two minutes wouldn’t have truly made a difference physiologically.
No matter what, be careful
In the end, it is important to remember that your performance will still likely be diminished from what you might have done in cooler conditions. If your race is an endurance race (gravel, gran fondo, TT, etc.), you will need to re-evaluate your pacing strategies, even if you are acclimatized. You should pace very conservatively early on until you have an idea on how your body is reacting to the heat. If you cannot control the pace of the race (ie a crit or road race) it is important to hydrate before and during the race. This well as keep your core temperature down.